Forest of Piano, known in Japan as Piano no Mori: ????? The Perfect World of Kai (The perfect world of KAI, lit. "Piano's Forest"), is a Japanese manga series written and illustrated by Makoto Isshiki. It was serialized by Kodansha from 1998 to 2015, initially in Young Magazine Uppers before transferring to Weekly Morning. Serialization is irregular, and went on hiatus in 2002 before resuming in 2006. The series ended after 26 bound volumes. The series was adapted into a 2007 Japanese animated feature film by director Masayuki Kojima and production company Madhouse. The film featured performances by the renowned pianist Vladimir Ashkenazy. An anime television series adaptation produced by Gaina premiered on April 9, 2018 on NHK.

Forest of Piano is a story that follows Kai Ichinose, a boy who lives in the red light district but escapes at night to play the piano in the forest. Shuhei Amamiya, the grade-school son of a professional pianist, transfers to Moriwaki Elementary, Kai's elementary school. But it doesn't take long before Shuhei is picked on by the class bullies, and gets involved in a dare to play the mysterious piano in the forest, leading to his meeting with Kai, who seems to be the only one capable of getting sound out of the thought-to-be broken piano. Kai's ability earns him the respect of Shuhei and his music teacher, former master pianist Sosuke Ajino. Both Shuhei and Ajino try to get Kai to take proper piano lessons, but Kai is at first resistant to refining his piano-playing technique. However, after hearing Sosuke play a Chopin piece he just can't seem to play himself, he relents.